ctpp-news August 2006

ctpp-news@mailman.chrispy.net

5 participants
12 discussions

by Chuck Purvis

Andy: I'll respond to CTPP-News since this is a good question and a tough answer. Yes, you can derive Group Quarters workers by Means of transportation by subtracting TOTAL workers by means, say, taking CTPP Table 1-20 (workers by means of transportation (11) by length of US residence) LESS CTPP Table 1-35 (workers in HHs by means of transportation to work (11) by vehicles available in HH). This should work, UNLESS you need detailed transit-sub-modes, or bike vs walk splits. No, you can't get average travel time, or GQ workers by travel time distribution (or even HH workers by travel time distribution) from the CTPP. The only method I'm aware of to obtain AVERAGE TRAVEL TIME for HOUSEHOLD WORKERS is from Census 2000 PUMS. Of course, with PUMS, you can estimate the average travel time, and the travel time distributions, for GQ workers as well as household workers. For our region, there is no difference in the average travel time for total workers compared to household workers, so for Average Travel Time it may not be worth the effort to do the calculation in PUMS. It's probably region-specific: how different are your GQ workers compared to HH workers? We would be in big trouble with our non-motorized lobby if we didn't separately report bicycle from walk commuters. So, what I did was use the bike/walk split for TOTAL commuters (say, CTPP Table 1-2, by 18 means of transportaiton), and applied the bike/walk split to the Household Workers shown in CTPP Table 1-35. Or, you could always use PUMS, but it's easier just to use the bike/walk split from CTPP Table 1-2. One thing you may want to try is to "age" the Census 2000 GQ data up to 2005, using the GQ population estimates that are available, at a county-level, from the FSCPE web site. It's an educated WAG, but it might be useful when you want to make comparisons to independent data, like the employed resident data from the BLS' LAUS estimates. Chuck ************************************************************** Charles L. Purvis, AICP Principal Transportation Planner/Analyst Metropolitan Transportation Commission 101 Eighth Street Oakland, CA 94607-4700 (510) 817-5755 (office) [new, 8/1/05] (510) 817-7848 (fax) [new, 8/1/05] www: http://www.mtc.ca.gov/ Census WWW: http://www.bayareacensus.ca.gov/ ************************************************************** >>> "Andrew PICKARD" <APICKARD(a)hrpdc.org> 08/31/06 1:57 PM >>> Very helpful post. Had a question for you. Do you know if there is a way to find out the number of group quarters workers, and their travel time and mode from 2000 Census? Just trying to get an idea of who we are missing in the 2005 ACS. Thanks for any assistance. Andy Pickard, P.E. Senior Transportation Engineer Hampton Roads Planning District Commission 723 Woodlake Drive Chesapeake, VA. 23320 Phone: 757.420.8300 Fax: 757.523.4881 apickard(a)hrpdc.org www.hrpdc.org

18 years, 2 months

ACS Data on Commuting

by Chuck Purvis

Greetings to CTPP-News: Well, this morning (August 29th) the Census Bureau released the socio-economic data tables from the 2005 American Community Survey (ACS2005). Some of the tables relevant to transportation planners & others are the journey-to-work related tables: workers by means of transportation; workers by travel time to work; and aggregate & average travel times. Users may also be interested in some of the limited "commute flow" data available: intra-place, intra-county, intra-MCD, commute-to-principal cities. The challenge is that the ACS2005 only includes data for persons-in-households, households, and workers-in-households. Comparable tables from Census 2000 aren't always that readily available. So, for HOUSEHOLD workers by means of transportation, we used CTPP Table 1-35, for Census 2000, to compare with the ACS. For HOUSEHOLD workers by travel time to work, we used Census 2000 PUMS; and for the average travel time by means of transportation for HOUSEHOLD workers, we also used Census 2000 PUMS. Comparable CTPP tables on household workers by travel time to work, or average travel time, are just not available. Data for our region (SF Bay Area) is included in the attached Excel workbook. The workbook contains: Table 1. Household Workers by Means of Transportation to Work by County of Residence, 2000 to 2005. Table 2. Household Workers by Travel Time to Work by County of Residence, 2000 to 2005. Table 3. Household Workers by Average Travel Time by Means of Transportation by County of Residence, 2000 to 2005. Table 1 is based on CTPP Table 1-35, Census 2000 PUMS (for bike/walk split for HH Workers), and ACS 2005, Table B08006. Table 2 is based on Census 2000 PUMS, and ACS 2005, Table B08012. Table 3 is based on Census 2000 PUMS, and ACS 2005, Table B08136. We are hard at work creating supplemental tables to report on the statistical significance of the differences. This is a chore as it requires calculating the standard errors for the Census 2000, and computing a z-statistic on the standard error of the difference between values. Z-statistics greater than 1.65 indicate a significant difference in the values or shares at the 90% confidence level; > 1.96 indicate a significant difference at the 95% confidence level, etc. What this does NOT do is calculate whether or not there is a "meaningful difference" between 2000 and 2005....That's more or less a professional judgment call. Data for Large Areas (65,000+ pop.) of WORK are expected for release on October 3rd (same release date for all of the household-related tables, including the household vehicle availability information.) PUMS. The ACS 2005 PUMS (Public Use Microdata Sample) was also released today, August 29th. Data is available in CSV and SAS format. The PUMS datasets appear complete (PUMA of Residence; POWPUMA - PUMA of Work appears to be the County of PUMA, whichever is larger, similar to Census 2000 PUMS....) The big headache with the ACS PUMS is that the Census Bureau has changed all of the variable names from a fairly mnemonic style to near gibberish: e.g., "JWTR" is the variable for "Means of transportation to Work", "COW" is for "Class of Worker" etc. Ah, well, we can adapt. It will be interesting to see the new stories emerging from this new set of ACS data. Stay tuned. cheers, Chuck Purvis, MTC ************************************************************** Charles L. Purvis, AICP Principal Transportation Planner/Analyst Metropolitan Transportation Commission 101 Eighth Street Oakland, CA 94607-4700 (510) 817-5755 (office) [new, 8/1/05] (510) 817-7848 (fax) [new, 8/1/05] www: http://www.mtc.ca.gov/ Census WWW: http://www.bayareacensus.ca.gov/ **************************************************************

18 years, 2 months

Re: [CTPP] ACS Data on Household Population compared to Independent Estimates: California/Bay Area

by Richard Lin

Dear Chuck, Very interesting of your comparisons. In order to have a fair evaluation, we need to have a list of assumptions (methods, procedures, etc) , input data (samples, indicators, etc), reference date (i.e. 1/1/05; 1/1/06; 7/1/2005; 2005 average; etc), and components (total pop, gq pop, household pop, household size; total housing units, occupied housing units, vacant housing units, vacancy rate) for comparisons. The 2004 (12-month) average ACS estimates provided estimates of total housing units and their implied vacancy rates but the 2005 ACS estimates do not have the data. We need to process the 2005 ACS PUMS file to figure out the size of samples for evaluation on the derived household sizes to see if the changes in household size are real. If we can get the numbers of vacant housing units (no response in ACS household survey) from the ACS PUMS samples, then we can calculate to obtain estimates of total housing units for comparison and for evaluation. We have collected some housing indicators (monthly BPUs, COUs, DMUs, and Others) from quite a few municipalities for estimating annual new housing units besides the USCB's (U.S. Census Bureau) annual BPU (Building Permit Units) survey data. It is very important to realize that we need a very good estimate of household population to fill into new housing units and should not apply a traditional housing unit method to use the number of new housing units to claim a certain numbers of household population. For instance you have picked 100 apples (persons) from your apple trees in your yard to fill your fruit baskets (housing units). It does not matter how many new fruit baskets you have brought with you, you still have only 100 apples to fill the baskets. Just please compile the annual (2000-2005) numbers of the U.S. population and numbers of the U.S. housing units for comparison and for analysis and you will get the right answers. Some of the 2005 ACS point population estimates are higher than that of our 7-1-2005 annual Colorado county and municipal population estimates but they are still falling within the lower and the upper bounds of 90% confidence interval. That means the differences are not statistically different at 90% confidence interval even though we are not satisfied with the conclusions. At least we can add the ACS survey estimates to our database for reference. Nice to share. - Richard Lin, Ph.D. Demographer Colorado Division of Local Government (303)866-4989, fax (303)866-2660 richard.lin(a)state.co.us >>> "Chuck Purvis" <CPurvis(a)mtc.ca.gov> 8/17/2006 9:33:53 AM >>> TO: CTPP-News Listserv FR: Chuck Purvis This is an email I prepared for our Bay Area and California Census listservs, regarding newly released ACS data. PLEASE, if there are other metro or state agencies who've analyzed the ACS household population relative to their independent estimates of household population, PLEASE share your research! * * * * * * * TO: Bay Area Census Listserv FR: Chuck Purvis, MTC The "first wave" of the American Community Survey data for 2005 was released yesterday, August 15th. This first year of the full ACS database EXCLUDES group quarters population, so any of the "TOTAL POPULATION" tables as shown by the Census Bureau's American FactFinder are actually "HOUSEHOLD POPULATION" (or population in households, whichever term you prefer.) The data for total population that INCLUDES group quarters will be included in the 2006 ACS data, to be released summer '07. Over the past year we have had concerns that the household population in the ACS (the 2004 ACS, to be particular), was significantly lower than decennial census counts of household population, and households. This is now a real concern with the 2005 ACS, as well. What we are able to compare for California is the household population estimates from the 2005 ACS, to our State Department of Finance's (DOF) estimates of total population, household population, GQ population, housing units, occupied housing units, at the city and county level, from their "E-5" estimate reports, available on the DOF web site (http://www.dof.ca.gov/HTML/DEMOGRAP/Druhpar.asp). There are standard errors in the DOF data, as suggested in their methodology, but DOF doesn't provide explicit confidence intervals around their estimates, at least as far as I could tell. So, I've been able to analyze the data for the 119 California Places (116 cities + 3 census designated places); and the 40 California Counties, that exceed the 65,000 household population threshhold for reporting ACS totals. I've also created tables for the San Francisco Bay Area Cities (25 cities) & Counties (9 counties) in the same EXCEL workbook. This EXCEL workbook is available from the MTC web site, at: ftp://ftp.abag.ca.gov/pub/mtc/planning/ACS/ Of the 119 California Places with household population estimates exceeding 65,000, thirteen of these cities are significantly different, comparing the 1/1/05 DOF (Department of Finance) household population, and the 1/1/06 DOF household population estimates, to the 95 percent confidence interval around the ACS household population estimates. Unfortunately this list includes six of the ten largest California Cities: 1. Los Angeles: ACS = 3,668 to 3,794 thousand; DOF = 3,852 to 3,892 thousand (estimates for 1/1/05 and 1/1/06) 2. San Diego: ACS = 1,176 to 1,240 thousand; DOF = 1,254 to 1,263 thousand 3. San Jose: ACS = 866 to 908 thousand; DOF = 931 to 943 thousand 4. San Francisco: ACS = 699 to 739 thousand (estimated); DOF = 773 to 778 thousand 8. Oakland: ACS = 355 to 393 thousand; DOF = 403 to 404 thousand 10. Santa Ana: ACS = 277 to 328 thousand; DOF = 345 to 346 thousand. The other seven California places with a significant difference, comparing ACS to our DOF, include: Garden Grove (Orange County); Salinas (Monterey County); Pasadena (LA County); Daly City (San Mateo County); Berkeley (Alameda County); Alhambra (LA County); and Merced (Merced County). A critical check in the coming months will be to compare the ACS estimates of housing units and households (occupied housing units) to independent estimates of housing units and households, also available from the DOF Report E-5. Perhaps the decline in population in these large California cities can be attributed to decreasing average household size. On the other hand, it is a lot harder to explain any absolute losses in housing units within a community. It may be useful for the City Planners in Large Cities to have at hand independent estimates of new housing units constructed and old housing units demolished over the 2000 to 2005 time period. These are very serious concerns about the ACS. I believe it has more to do with the "sample frame" and weighting/expansion issues, as opposed to the quality of the characteristics derived from the ACS, but this is an important topic that should be discussed by our state data center network, the Census Bureau and interested stakeholders. Hope this helps, Chuck Purvis ************************************************************** Charles L. Purvis, AICP Principal Transportation Planner/Analyst Metropolitan Transportation Commission 101 Eighth Street Oakland, CA 94607-4700 (510) 817-5755 (office) [new, 8/1/05] (510) 817-7848 (fax) [new, 8/1/05] www: http://www.mtc.ca.gov/ Census WWW: http://www.bayareacensus.ca.gov/ ************************************************************** _______________________________________________ ctpp-news mailing list ctpp-news(a)chrispy.net http://www.chrispy.net/mailman/listinfo/ctpp-news

18 years, 2 months

Further examination of ACS 2005 data for California

by Chuck Purvis

I'm cross-posting this message to our local, state, and national census listservs. I've updated our analysis of the 40 California Counties and 119 California Places with (household) population greater than 65,000. An excel workbook is on our web site, at: ftp://ftp.abag.ca.gov/pub/mtc/planning/ACS/ filename: California_ACS_compared2_CalifDOF.xls Table 1. Comparing Bay Area County Household Population: ACS2005 to DOF2005/06 (DOF = California State Department of Finance, our State Data Center) Table 2. Comparing Bay Area City Household Population: ACS2005 to DOF2005/06 Table 3. Comparing California County Household Population: ACS2005 to DOF2005/06 Table 4. Comparing California City Household Population: ACS2005 to DOF2005/06 Table 5. Compare Households, Household Population and Average Household Population (new, 8/18) One of our principal concerns is that there is a significant difference in household population - - comparing the ACS2005 data to our independent (Calif State DOF) estimates of household population - - in 13 of the 119 California Cities covered in the ACS2005 data, released this past Tuesday, 8/15. Six of the largest ten California cities are on this list: Los Angeles, San Diego, San Jose, San Francisco, Oakland, and Santa Ana. (Three of these: SF, SJ and Oakland, are in my region....) So, why the difference? 1. The ACS2005 is controlled at the county-level to the FSCPE population estimates. (FSCPE = Federal-State Cooperative Program for Population Estimates). These FSCPE county-level files are available here: http://www.census.gov/popest/datasets.html More on the FSCPE program here: http://www.census.gov/population/www/coop/fscpe.html Note that these FSCPE estimates include county- and state-level values for total population, household population and group quarters population. Also note that the FSCPE does not include estimates of either occupied dwelling units (households) or total units (occupied + vacant). 2. Our California State Department of Finance current population estimates (their "E-5" report series) is available here: http://www.dof.ca.gov/HTML/DEMOGRAP/ReportsPapers/Estimates/E5/E5-06/E-5tex… The California State DOF forecasting methodology is described in the above URL, and discusses the "housing unit method" used by DOF in some detail. (Makes good sense to me!) 3. Population estimates produced by the States may be different than population estimates produced by the Census Bureau. An excellent, insightful and educational article on current population estimates is included in the July-August 2006 edition of the APDU (Association of Public Data Users) newsletter, available here: http://www.apdu.org/. This article discusses a one-day conference on 7/19/06 co-hosted by COPAFS (Council of Professional Associations on Federal Statistics) and Sabre Systems. This is a must read for anyone interested in understanding possible issues in the control totals used in weighting/expanding ACS data. 4. What to do next? My recommendation is to be patient, and wait for the "total housing unit" data from ACS2005, expected for release this October 3rd. This will be the best information that city and county planners will have, when comparing ACS estimates of housing units to any independent estimates of housing units. The Table 5 in my XLS workbook is very revealing: the ACS is extremely valuable in indicating significant changes in average household size: San Jose's average household size is declining from 3.20 to 3.08; San Francisco from 2.31 to 2.23; and Oakland from 2.60 to 2.56. These are plausible trends, and trends we would not have predicted without the ACS. On the other hand, it appears that the ACS may be showing a 2.2 percent LOSS in the San Francisco City housing stock (actually, households derived by: household population divided by average household size, as published in American Factfinder); and a 3.1 percent LOSS in the Oakland City housing stock, 2000 to 2005. (To put this loss of 4,700 housing units in Oakland in perspective, this 4,700 housing unit loss is 1.6 times as high as the 2,900 housing units we lost in the 1991 Oakland Firestorm....) The fact of the matter is that housing units are a fairly durable good, and they don't disappear that easily. So, my conclusion is that improvements are needed in the FSCPE population estimates to incorporate changes in housing stock. Easier said than done, so it may be a few years before our housing numbers recover.... Hope this is helpful to the SDC networks and others, Chuck Purvis, Metropolitan Transportation Commission, Oakland, California (Affiliate Data Center in the San Francisco Bay Area) ************************************************************** Charles L. Purvis, AICP Principal Transportation Planner/Analyst Metropolitan Transportation Commission 101 Eighth Street Oakland, CA 94607-4700 (510) 817-5755 (office) [new, 8/1/05] (510) 817-7848 (fax) [new, 8/1/05] www: http://www.mtc.ca.gov/ Census WWW: http://www.bayareacensus.ca.gov/ **************************************************************

18 years, 2 months

ACS Data on Household Population compared to Independent Estimates: California/Bay Area

by Chuck Purvis

TO: CTPP-News Listserv FR: Chuck Purvis This is an email I prepared for our Bay Area and California Census listservs, regarding newly released ACS data. PLEASE, if there are other metro or state agencies who've analyzed the ACS household population relative to their independent estimates of household population, PLEASE share your research! * * * * * * * TO: Bay Area Census Listserv FR: Chuck Purvis, MTC The "first wave" of the American Community Survey data for 2005 was released yesterday, August 15th. This first year of the full ACS database EXCLUDES group quarters population, so any of the "TOTAL POPULATION" tables as shown by the Census Bureau's American FactFinder are actually "HOUSEHOLD POPULATION" (or population in households, whichever term you prefer.) The data for total population that INCLUDES group quarters will be included in the 2006 ACS data, to be released summer '07. Over the past year we have had concerns that the household population in the ACS (the 2004 ACS, to be particular), was significantly lower than decennial census counts of household population, and households. This is now a real concern with the 2005 ACS, as well. What we are able to compare for California is the household population estimates from the 2005 ACS, to our State Department of Finance's (DOF) estimates of total population, household population, GQ population, housing units, occupied housing units, at the city and county level, from their "E-5" estimate reports, available on the DOF web site (http://www.dof.ca.gov/HTML/DEMOGRAP/Druhpar.asp). There are standard errors in the DOF data, as suggested in their methodology, but DOF doesn't provide explicit confidence intervals around their estimates, at least as far as I could tell. So, I've been able to analyze the data for the 119 California Places (116 cities + 3 census designated places); and the 40 California Counties, that exceed the 65,000 household population threshhold for reporting ACS totals. I've also created tables for the San Francisco Bay Area Cities (25 cities) & Counties (9 counties) in the same EXCEL workbook. This EXCEL workbook is available from the MTC web site, at: ftp://ftp.abag.ca.gov/pub/mtc/planning/ACS/ Of the 119 California Places with household population estimates exceeding 65,000, thirteen of these cities are significantly different, comparing the 1/1/05 DOF (Department of Finance) household population, and the 1/1/06 DOF household population estimates, to the 95 percent confidence interval around the ACS household population estimates. Unfortunately this list includes six of the ten largest California Cities: 1. Los Angeles: ACS = 3,668 to 3,794 thousand; DOF = 3,852 to 3,892 thousand (estimates for 1/1/05 and 1/1/06) 2. San Diego: ACS = 1,176 to 1,240 thousand; DOF = 1,254 to 1,263 thousand 3. San Jose: ACS = 866 to 908 thousand; DOF = 931 to 943 thousand 4. San Francisco: ACS = 699 to 739 thousand (estimated); DOF = 773 to 778 thousand 8. Oakland: ACS = 355 to 393 thousand; DOF = 403 to 404 thousand 10. Santa Ana: ACS = 277 to 328 thousand; DOF = 345 to 346 thousand. The other seven California places with a significant difference, comparing ACS to our DOF, include: Garden Grove (Orange County); Salinas (Monterey County); Pasadena (LA County); Daly City (San Mateo County); Berkeley (Alameda County); Alhambra (LA County); and Merced (Merced County). A critical check in the coming months will be to compare the ACS estimates of housing units and households (occupied housing units) to independent estimates of housing units and households, also available from the DOF Report E-5. Perhaps the decline in population in these large California cities can be attributed to decreasing average household size. On the other hand, it is a lot harder to explain any absolute losses in housing units within a community. It may be useful for the City Planners in Large Cities to have at hand independent estimates of new housing units constructed and old housing units demolished over the 2000 to 2005 time period. These are very serious concerns about the ACS. I believe it has more to do with the "sample frame" and weighting/expansion issues, as opposed to the quality of the characteristics derived from the ACS, but this is an important topic that should be discussed by our state data center network, the Census Bureau and interested stakeholders. Hope this helps, Chuck Purvis ************************************************************** Charles L. Purvis, AICP Principal Transportation Planner/Analyst Metropolitan Transportation Commission 101 Eighth Street Oakland, CA 94607-4700 (510) 817-5755 (office) [new, 8/1/05] (510) 817-7848 (fax) [new, 8/1/05] www: http://www.mtc.ca.gov/ Census WWW: http://www.bayareacensus.ca.gov/ **************************************************************

18 years, 2 months

Association of Public Data Users' conference

by Patty Becker

>The Association of Public Data Users is a group >of users users and producers of federal data >that works together to improve the quality, >accessibility, and usefulness of federal >data. This group will be having its 2006 >Conference in Alexandria, Virginia during >October. The conference is described below and >a copy of the conference brochure and registration form is attached. > > >APDU 2006 Annual Conference > > > >Navigating Rivers of Data > > > >Thurs., October 5 Fri., October 6, 2006 >Embassy Suites Hotel >Alexandria Old Town, Virginia > > > > ><http://www.apdu.org/conference/2006/index.htm>www.apdu.org/conference/2006/index.htm > >Important Deadlines! > >Tues., Sept. 5 -- deadline for hotel reservations at conference rate > >Fri., Sept. 15 deadline for conference registration at the reduced rate > >The annual conference of the Association of >Public Data Users offers a collegial forum for >data users, producers and intermediaries to >exchange information, share perspectives on data >and public policy issues, and explore critical >data sources and user applications. > >Over two days of plenary sessions, APDU 2006 >attendees will hear from noted speakers on a >range of factors influencing the collection, >availability and application of public data. >Join us for updates on federal executive and >legislative activities, the latest information >on Census 2010 planning and the American >Community Survey, overviews of pertinent and >innovative data collections, and much more! > >For session and speaker information and updates, >see ><http://www.apdu.org/conference/2006/agenda.htm>www.apdu.org/conference/2006/agenda.htm >----------------------------- >Register before Sept. 15, and enjoy the entire >conference at the reduced rate of $350 for APDU >members, $450 for non-members. Thats a savings >of $25 from the rate in effect after the 15th. >Fees include all sessions, lunches, breaks, reception and conference materials. > >Download registration forms at ><http://www.apdu.org/conference/2006/register.htm>www.apdu.org/conference/2006/register.htm >-------------------------------- >This years conference venue is the Embassy >Suites Hotel, 1900 Diagonal Rd., Alexandria >Old Town, Va. (703-684-5900) located across from >the King Street metro station. Room rates are >$199/night, plus tax. Make your reservations by >Sept. 5, and mention you are associated with APDU. > >For more information, see ><http://www.apdu.org/conference/2006/hotel.htm>www.apdu.org/conference/2006/hotel.htm >-------------------------------- >Have questions? > >Contact Patricia Becker, APDU Administrator, >248-354-6520, <mailto:info@apdu.org?subject=APDU%202006>info(a)apdu.org > >Association of Public Data Users >c/o APB Associates >28300 Franklin Road >Southfield, Michigan 48034-1657 > =============================== Patricia C. (Patty) Becker 248/354-6520 APB Associates/SEMCC FAX 248/354-6645 28300 Franklin Rd Home 248/355-2428 Southfield, MI 48034 pbecker(a)umich.edu

18 years, 2 months

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ctpp-news August 2006